Redox Reactions Test

Result

Redox Reactions Test - 52

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Weekly Quiz Competition

Question 1
1 / -0

Oxidation number of sodium in sodium amalgam is:

A
+2

B
+1

C
-3

D
0
Question 2
1 / -0

Which of the following shows highest oxidation number in combined state?

A
$$O$$

B
$$Ru$$

C
Both $$(A)$$ and $$(B)$$

D
None of the above

Solution

The possible oxidation states shown by :-
$$(O)$$ Oxygen $$\rightarrow$$ $$-2,-1,0,+1,+2$$
$$(Ru)$$ Ruthenium $$\rightarrow$$ $$-4,-2,0,+1,+2,+3,+4,+5,+6,+7,+8$$
Therefore, ruthenium $$(Ru)$$ shows highest oxidation number i.e. $$+8$$ in combined state.
Question 3
1 / -0

$${ I }_{ 2 }+KI\rightarrow { KI }_{ 3 }\quad $$
In the above reaction:

A
only oxidation takes place

B
only reduction takes place

C
both of the above

D
none of these

Solution

$${ \overset { 0 }{ I } }_{ 2 }+K\overset { -1 }{ I } \longrightarrow K{ \overset { -1 }{ I } }_{ 3 }$$
Here, only $${ \overset { 0 }{ I } }_{ 2 }$$ is reduced to $$K{ \overset { -1 }{ I } }_{ 3 }$$ and no other effect takes place.
Therefore, only reduction takes place.
Question 4
1 / -0

Oxidation state of oxygen in hydrogen peroxide is?

A
-1

B
+1

C
0

D
-2

Solution

Hydrogen peroxide $$={ H }_{ 2 }{ O }_{ 2 }$$
$$\overset { +1 }{ H } -\overset { -1 }{ O } -\overset { -1 }{ O } -\overset { +1 }{ H } $$
Here, the oxidation states of hydrogen is $$+1$$ and that of oxygen atoms is $$-1$$.
Question 5
1 / -0

Oxidation number of sulphur in $$Na_2S_2O_3$$ would be :

A
+4

B
+2

C
-2

D
0

Solution

$${ Na }_{ 2 }{ S }_{ 2 }{ O }_{ 3 }\Rightarrow $$
Oxidation number of $${ S }_{ 1 }=-2$$
Oxidation number of $${ S }_{ 2 }=+1+1+2+2=+6$$
Average oxidation number of $$S=\dfrac { -2+6 }{ 2 } =+2$$
Question 6
1 / -0

The oxidation state of Al in $$LiAlH_4$$ is:

A
zero

B
$$+1$$

C
$$+2$$

D
$$+3$$

Solution

$${ LiAlH }_{ 4 }\longrightarrow { Li }^{ + }\left[ { AlH }_{ 4 }^{ - } \right] $$
Let the oxidation state of $$Al$$ be $$x$$
Since hydrogen is more electronegtive than aluminium, thus the oxidation state of $$H$$ will be taken as $$-1$$.
The oxidation state of $$H$$ in $${ AIH }_{ 4 }^{ - }$$ is $$-1$$
$$\therefore$$ For $${ AIH }_{ 4 }^{ - }\quad \Rightarrow \quad x+4\left( -1 \right) =-1$$
$$x-4=-1$$
$$\boxed { x=+3 } $$
Therefore, the oxidation state of $$AI$$ in $${ LiAIH }_{ 4 }$$ is $$+3$$.
Question 7
1 / -0

Which of the following shows highest oxidation number in combined state?

A
$$Os$$

B
$$Ru$$

C
Both (1) & (2)

D
None

Solution

The possible oxidation states of $$Os$$ and $$Ru$$ are :-
$$Os \Rightarrow -4,-2,-1,0,+1,+2,+3,+4,+5,+6,+7,+8$$
$$Ru \Rightarrow -4,-2,0,+1,+2,+3,+4,+5,+6,+7,+8$$
Therefore, both $$Os$$ and $$Ru$$ show highest oxidation number of $$+8$$.
Therefore, $$(C)$$ is the correct answer.
Question 8
1 / -0

In $$Ni{(CO) }_{ 4 }$$ the oxidation state of Ni is:

A
4

B
0

C
2

D
8

Solution

Let the oxidation state of $$Ni$$ be $$x$$.
The oxidation states of $$CO$$ is $$0$$.
$$\therefore$$ $$x+0=0$$
$$\therefore$$ $$x=0$$
Hence, the oxidation state of $$Ni$$ in $${ Ni\left( CO \right) }_{ 4 }$$ is zero.
Question 9
1 / -0

In acidic medium $$H_{2}O_{2}$$ changes $$Cr_{2}O_{7}$$ to $$CrO_{5}$$ which has two $$-O-O-$$ bonds. Oxidation state of $$Cr$$ in $$CrO_{5}$$ is:

A
$$+6$$

B
$$-10$$

C
$$+5$$

D
$$+3$$

Solution

1) Since, $$Cr$$ has only five electrons in $$3d$$ orbitals and one electron in $$4s$$ orbital.
2) This exceptional value is due to the fact that four oxygen atoms in$$ CrO_5 $$are in peroxide linkage.
3)The chemical structure of $$CrO_5$$ is $$ x – 2 – 4 = 0$$ or $$x = + 6.$$
Question 10
1 / -0

Reaction in which exactly two carbons are oxidized ?

A
Reaction of Pentan-3-one with $$CH_{3}CO_{3}H$$

B
Reaction of acetone with NAOH/$$I_{2}$$

C
Reaction of propene with $$Br_{2}$$

D
Reaction of $$(CH_{3})_2$$$$(CH_{3})_2C$$= NOH with $$H_{2}So_{4}$$

Solution

$$\mathrm{CH}_{3} \mathrm{COCH}_{3} \frac{4 \mathrm{NaOH}}{3 \mathrm{I}_{2}} \rightarrow \mathrm{CHI}_{3}+3 \mathrm{NaS}+$$
Acetone $$ \mathrm{CH}_{3} \mathrm{COONa}+3 \mathrm{H}_{2} \mathrm{O} $$
$$ \begin{array}{l} \text { two carbons are oxidised in this reaction .} \\ \text { so, Reaction of acetone with NAOH } / \mathrm{I}_{2} \\ \text { is correct answer. } \end{array} $$

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Re-Attempt Weekly Quiz Competition

Redox Reactions Test - 52

Result

Redox Reactions Test - 52

Score

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Rank

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SHARING IS CARING

Question 1

+2

+1

-3

0

Question 2

$$O$$

$$Ru$$

Both $$(A)$$ and $$(B)$$

None of the above

Solution

Question 3

only oxidation takes place

only reduction takes place

both of the above

none of these

Solution

Question 4

-1

+1

0

-2

Solution

Question 5

+4

+2

-2

0

Solution

Question 6

zero

$$+1$$

$$+2$$

$$+3$$

Solution

Question 7

$$Os$$

$$Ru$$

Both (1) & (2)

None

Solution

Question 8

4

0

2

8

Solution

Question 9

$$+6$$

$$-10$$

$$+5$$

$$+3$$

Solution

Question 10

Reaction of Pentan-3-one with $$CH_{3}CO_{3}H$$

Reaction of acetone with NAOH/$$I_{2}$$

Reaction of propene with $$Br_{2}$$

Reaction of $$(CH_{3})_2$$$$(CH_{3})_2C$$= NOH with $$H_{2}So_{4}$$

Solution

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